1. Field of the Invention
The present invention relates to a technology for changing capacity of a path group of a lower layer according to the traffic in an upper layer in a hierarchical network in which a link of the upper layer is accommodated with the path group of the lower layer.
2. Description of the Related Art
As traffic of data communications such as on the Internet increases, the requirement for a large-sized large capacity network is changing. In a conventional circuit switching network, it is possible to design the capacity of paths that accommodate circuits connecting between switching nodes beforehand in consideration of the number of subscribers, so that capital investment can be planned according to demand.
In the circuit switching type network, the capacity of a link connecting nodes is always planned beforehand, and the speed of change and update of the capacity is very low. Therefore, the frequency of change of link capacity is very small. The circuit switching network infrastructure and the operation system are designed on the understanding of it.
On the other hand, in a network for data communication, there are various drastically variable factors. Some examples are establishment or retirement of an Internet service provider, remote database backup by mirroring between various servers and the like. The speed of capacity update for the circuit switching network cannot follow the change of capacity of the network for data communication. Thus, for designing a circuit switching network that accommodates a network for data communication, the capacity is determined so as to allow for future increase of capacity.
However, the network for data communication in which the traffic changes in a short period does not conform to the circuit switching network, so that it is not efficient to use the circuit switching network as a lower layer network of the network for data communication.
That is, in many cases, a network for data communication such as an IP (Internet Protocol) network and an Ethernet network uses an SDH (Synchronous Digital Hierarchy) network that is a circuit switching network as a lower layer network for transmitting traffic. In the SDH network, a start node and an end node are determined and a path is set up and fixed. Once the path is set up, a constant capacity is maintained in the network, in which changing the capacity and the route of the path takes much time, so that the frequency of the change is low.
When the IP network and the Ethernet network and the like are used as the upper layer network, and the SDH network is used as the lower layer network, the network configuration is layered and management is performed for each layer network separately. Thus, for changing the bandwidth of the network, settings must be changed not only for the network of the upper layer but also for the network of the lower layer. Thus, it takes much time to change the network configuration. Therefore, the capacity of the network of the lower layer is designed with an adequate margin. As a result, the network resources can not be used efficiently.
Recently there is a possibility that a network such as an optical cross connect network that carries traffic by each wavelength can be used as a next generation lower layer network. However, currently, setting up or tearing down a path of the optical network is performed by using the same method as that used for the conventional SDH network. Therefore, even though the next generation lower layer network is used, the capacity for the lower layer network is designed to have an adequate margin.
Recently, Generalized-MPLS (Generalized-Multiprotocol Label Switching) is being proposed in standardization organizations such as OIF/IETF and the like. The Generalized-MPLS is an expanded version of MPLS that is a connection type networking technology. In the Generalized-MPLS, the MPLS is expanded to the circuit switching layer such as ATM (Asynchronous Transfer Mode)/SDH/SONET (Synchronous Optical Network) or the optical layer. The Generalized-MPLS manages Virtual Path (VP) provided in the ATM layer, SDH path provided in the physical layer, wavelength path provided in the optical layer and optical fiber together. This technology aims to provide services flexibly by using the unified control method of the ATM apparatus, the SONET/SDH apparatus, the WDM apparatus, the optical cross connect apparatus and the fiber switch that are conventionally managed separately for each layer. In addition, the technology aims to prevent redundancy for capacity design for each layer and to provide services speedily. In the specification of OIF-UNI 1.0, it is described that policy control is applied to use of network resources by using a policy server.
However, the technologies such as the above-mentioned G-MPLS do not-have a mechanism for changing a link capacity flexibly according to amount of traffic. Therefore, even if the technologies are used, the problem that network resources are not used efficiently is not solved.
That is, G-MPLS cannot control the capacity of the lower layer network according to the change of the amount of traffic. Therefore, when a network such as an IP network and an Ethernet network is accommodated as the upper layer network, it is necessary to make allowance for future traffic increase of the upper layer network. It is necessary to forecast maximum amount of traffic in the path of the lower layer network, so that the path is set up semipermanently considering an adequate margin for the maximum future amount of traffic. Therefore, in the SDH network, it is necessary to prepare network resources having capacity much larger than the total amount of traffic actually being carried, which is inefficient from the viewpoint of use of network resources.
As mentioned above, according to the conventional technology, since the capacity of the path of the lower layer is constant, when the amount of traffic is small, a large part of resources of the lower layer is wasted. In addition, when the amount of traffic increases in a burst, the capacity of the network may become deficient so that a part of the traffic may be lost. In the G-MPLS, a mechanism is proposed in which a path is set up in the lower layer according to a request from the upper layer. However, in the mechanism, the capacity in the lower layer is not controlled proactively according to the amount of traffic of the upper layer. In addition, there is a conventional technology disclosed in Japanese laid-open patent application No.13-333045.